Various medical procedures can include penetrating the skin with a probe, such as a needle or a catheter. For example, spinal anesthesia or a spinal diagnostic procedure can include percutaneous delivery of anesthetic to an epidural location or sampling of spinal fluid. Such spinal anesthesia or spinal diagnostic procedures generally include penetrating the ligamentum flavum, a ligament between the spinous processes lateral to the dura. Generally, a desired final needle position during epidural placement is lateral the dura, while in a spinal tap, the dura is penetrated in order to obtain fluid from the spinal cavity.
Spinal taps have several important clinical applications including sampling cerebral spinal fluid (CSF), administering chemotherapy or other drugs directly into the spinal cavity, or relieving pressure in the spinal cavity for cardiac procedures. Sampling of CSF can also be necessary to quickly diagnose various diseases such as meningitis. Other procedures can similarly include penetrating the skin with a probe, such as paravertebral somatic nerve blockade (PVB).